Garda Commissioner Noirin O'Sullivan has warned that it is inevitable more bad practice in the force will emerge as she deals with the fallout over non-existent drink-driving tests.

Watchdogs have called ethics standards among gardai into question after an audit revealed gross exaggeration of the numbers of drivers being breathalysed.

Ms O'Sullivan addressed the issue publicly for the first time and warned it was unacceptable.

"This is an issue - as the Authority has pointed out - which is more than systemic," she said.

"It's about ethics. It's about supervision. It's about measurement. Most of all, it's about trust."

The scale of the issue was revealed during the week with almost one million fewer breath tests carried out than the force recorded.

Some 14,700 drivers have been taken to court - mostly for not displaying tax and insurance discs - without being given an opportunity to pay a penalty.

Ms O'Sullivan has called in the Garda Inspectorate to carry out a review.

"What we've found thus far is totally unacceptable and not in keeping with the standards of a modern and professional police service," she said.

The Commissioner said the issue was a matter of "individual and collective ethical behaviour and not one of occasional systems failure".

She said: "It is a matter of grave disappointment that this has apparently been happening for so long, unchallenged."

It is not the first time the Garda's record keeping has been called to account.

Last year, official analysis by the Central Statistics Office found almost a fifth of crime reported to the force was not recorded on its own system.

It also said the force's success rate in solving crimes is probably 10% lower than claimed.

In 2015, the CSO said almost a fifth of crimes reported to the Garda in 2011 were not recorded on the Pulse database.

That followed a damning audit by the Garda Inspectorate, published in 2014, that exposed massive errors on the Pulse system including poor classification of incidents and under-reporting casting doubt on the country's true crime rates.

The watchdog concluded that it was difficult to determine the scale of unrecorded crime but it could be about a quarter of offences.

Ms O'Sullivan said the public will be reassured.

"However, it is important to state at this point that when an organisation like An Garda Siochana is on a journey of radical reform, as it is under my commissionership, it is inevitable that we will identify more examples of bad practice," she said.

"In addition to correcting these issues, we must share that information, no matter how negative it is, not just with the authority, but also with the public.